The wavelength of a light beam is doubled. Which one of the following is correct for the momentum of photons for that light beam?
A) It is halved.
B) It stays the same.
C) It is doubled.
D) It is reduced by one-fourth
E) It is quadrupled.

Question

Quizplus · Accepted Answer

The momentum of a photon is given by p = h/λ, where h is Planck's constant and λ is the wavelength of the light. Doubling the wavelength means that the denominator of this equation is doubled, so the momentum will be halved (since it is inversely proportional to the wavelength). Therefore, the correct answer is A) it is halved.

The Wavelength of a Light Beam Is Doubled